Influence of Meteorological Factors on the Potential Evapotranspiration
in Yanhe River Basin, China
Potential evapotranspiration (ET0) is an
essential component of the hydrological cycle, and quantitative
estimation of the influence of meteorological factors on
ET0 can provide a scientific basis for studying
the impact mechanisms of climate change. In the present research, the
Penman-Monteith method was used to calculate ET0.
The Mann-Kendall statistical test with the inverse distance weighting
were used to analyze the spatiotemporal characteristics of the
sensitivity coefficients and contribution rates of meteorological
factors to ET0 to identify the mechanisms
underlying changing ET0 rates. The results showed
that the average ET0 for the Yanhe River Basin,
China from 1978–2017 was 935.92 mm. Save for a single location
(Ganquan), ET0 increased over the study period.
Generally, the sensitivity coefficients of air temperature (0.08), wind
speed at 2 m (0.19), and solar radiation (0.42) were positive, while
that of relative humidity was negative (-0.41), although significant
spatiotemporal differences were observed. Increasing air temperature and
solar radiation contributed 1.09% and 0.55% of the observed rising
ET0 rates, respectively; whereas decreasing wind
speed contributed -0.63%, and relative humidity accounted for -0.85%.
Therefore, it was concluded that the decrease of relative humidity did
not cause the observed ET0 increase in the basin.
The predominant factor driving increasing ET0 was
rising air temperatures, but this too varied significantly by location
and time (intra- and interannually). Decreasing wind speed at Ganquan
Station decreased ET0 by -9.16%, and was the
primary factor underlying the observed, local “evaporation paradox.”
Generally, increases in ET0 were driven by air
temperature, wind speed and solar radiation, whereas decreases were
derived from relative humidity.